Antistatic agents



United States Patent 3,399,178 ANTISTATIC AGENTS Christos Savides, Piscataway Township, Middlesex County, N.J., and John Edward Milks, Stamford, Conm, assigners of one-half to American Cyanamid Company, Stamford, Conn, a corporation of Maine and one-half to Arizona Chemical Company, New York, N.Y., a

corporation of Delaware No Drawing. Filed Sept. 1, 1965, Ser. No. 484,422 8 Claims. (Cl. 260-895) This invention relates to a method for imparting antistatic properties to polymeric compositions and, more particularly, to a method for minimizing the accumulation of static electricity'in polymers such as polyolefins, vinyl chloride polymers, styrene polymers, acrylic polymers, etc. The method involves incorporating in the polymer a compound represented by the following Formula I:

wherein R is an aliphatic or a cycloaliphatic radical of eight to nineteen carbon atoms (straight or branched); R is a lower alkyl radical of 1-3 carbons; R" and R are either hydrogen or alkyl of 1-4 carbons; and X is an anion. It relates further to the polymeric compositions resulting fromthis method.

Polymeric plastic compositions typified by polymers of monoolefins (e.g., homopolymers and copolymers of ethylene, propylene and butylene) tend to accumulate surface electric charges during fabrication, and, subsequently, during the life of the material. This is highly objectionable for a number of reasons. Charged bodies attract dust, and, depending upon conditions, may also cause other troublesome effects such as shock to the person contacting the charged material, radio interference, etc.

Various means have been proposed to overcome or minimize the accumulation of surface electric charges including surface application of various types ofantistatic materials, e.g., quaternary ammonium salts. However, surface treatment is often of only temporary assistance. Application of a coating composition containing an antistatic agent, has also been proposed, but coating processes are costly and the effect is not permanent.

It has also been proposed to incorporate the antistatic agent into the plastic composition during either compounding molding or fabrication steps. For practical purposes, an antistatic agent which is to be used by incorporation directly into the plastic, must fulfill certain requirements. To begin with, the agent must have sufficient antistatic activity'when applied at feasible concentrations. Thusfthe agent should be effective at low concentrations for reasons of economy and, in addition, to avoid impairing the properties of the polymeric substrate. The material must be compatible with the plastic composition and must be of such a nature that it can be easily incorporated during the conventional compounding and milling steps. The antistatic properties of the agent should be substantially permanent and should outlast exposure to high temperatures. Heat stability is especially important for use in polypropylene which must be heated to high temperatures to enable proper compounding, milling and molding thereof.

. Materials have previously met certain of these requirements to varying degrees. However, there isstill a definite need for a practical antistatic agent which is effective at low concentrations and has good heat stability so that its efiect is not destroyed during the processing steps.

The present invention is based on the discovery that the ice quaternary alkyl ammonium esters defined by Formula I meet the stated requirements for useful antistatic agents. Thus, members of this class are highly active in polyolefins at low concentrations. The antistatic agents of this invention are effective even at concentrations as low as about 0.1% based on the weight of the polymer. Higher concentrations up to about 5% are also useful for specialized requirements. For-normal applications, they are used in concentrations of 0.3% to 2.0%. The matter of choosing a concentration to fit a particular need will be easily dealt with by the ordinarily skilled artisan.

A surprising feature of the antistatic agents of this invention is their uniquely high thermal stability. As stated above,-heat stability is an important requirement for useful plastic antistatics. The compounds of this invention are definitely superior in this respect to previous antistatic compounds. This property can be demonstrated in different ways, such as by noting the progressive decomposition of the compound itself as evidenced by loss in weight when subjected to increasingly high temperatures; or by noting the discoloration or decomposition of a plastic composition containing the antistatic compound. In some instances, when the composition containing the antistatic compound is subjected to progressively increasing temperatures, the antistatic agent accelerates the decomposition of the plastic. With the agents of this invention, this effect is greatly minimized.

Several methods are available for evaluation of the compounds of the invention as antistatics. Molded or extruded formulations of the polyolefins containing a known amount of the antistatic agents are prepared and these are then evaluated for heat stability, surface resistivity, and presence and strength of surface static charge. A rough preliminary test of the antistatic properties of the compound consists of wetting a strip of acrylic paper with the surface resistivity of the dried strip after it has been a solution of the compound in isopropanol and measuring subjected to a high potential.

The antistatic agents defined by Formula Ican be prepared by reacting a glycidyl ester (II) with a secondary amine (III) to give a hydroxy amino ester (IV) which is then quaternized in the usual manner.

The symbols R, R, R", R and X are as defined above. The reaction to produce IV can be conducted with or with out a solvent, at elevated temperature (i.e., temperatures in the range of about 50 to C.). No catalyst is necessary, and about one mole of amine, for each mole of glycidyl ester, should be employed.

Compound IV can be isolated from the reaction product by distillation procedures, and then quaternized by treatment with conventional alkylating agents to give the'deamples in which parts and percentages are on a weight sired antistatic agent. basis. 7 V 7 H M Advantageously, startingmater'ials for the foregoing EXAMPLE 1 reactions are generally available on a commercial basis. They may be either synthetic materials or derived from natural sources. In general, the natural materials are mix- Evaluation of antistatic agents in polyvinyl chloride tures of acids of varying chain length, although single (1) SAMPLE PREPARATION component natural materials are also useful.

Among the useful glycidyl esters are glycidyl palmitate, The additives were incorporated into polyvinyl chloride glycidyl stearate, glycidyl laurate, glycidyl oleate, gylcidyl by milling on a two-roll laboratory millat 175 C at linoleate, glycidy-l linoleneate and glycidyl esters of such 1.5% concentration for fi ve minutes. The milled sheet obmixed acids as coconut oil fatty acids (predominantly tained was compression-molded at.l 7.0l7 5 C. and under lauric acid having other C -C acidic components), tall 24 tons pressure into plaques 2 x 2 /2 x 0.050'inches.

oil fatty acids (mainly C mixed saturated, unsaturated,

polyunsaturated acids such as oleic, linoleic and linolenic I (2) TEST METHODS acids), Cg-Cu neo-carboxylic acids and rosin acids (main- H I ly abietic acid and partially hydrogenated derivatives). (a) Resistivity measurements. Surface resistivity Useful amines for preparing the hydroxyamino esters of measurements were made according to a modified ASTM Formula IV are di(fi-hydroxyalkyl)amines in which the D257-58 using a Tera-Ohmmeter (Rhode and Schwartz alkyl groups have 16 carbons. Especially useful are sec- Co.) at 900 volts.

ondary amines having either hydroxyethyl or hydroxy- Surface resistivity, expressed as megohms (instrument propyl substituents. reading) is defined as the ratio of the direct voltage (900 Useful quaternizing agents are the conventional alkylatvolts) to the current on the surface of the polymer saming agents such as the lower dialkylsulfates (e.g., dimethyl ple when the electrodes of the Tera-Ohmmeter are placed sulfate, diethyl sulfate, etc.), methyliodide, ethyliodide, 25 on opposite sides of the sample.

etc. All samples were conditioned for at least 24 hours at The quaternary compounds of Formula I as well as the 70 F. and 50% relative humidity and the measurements hydroxyamino esters of Formula IV undergo reversible were made under the above conditions; low resistivity transesterification reactions so that upon standing, instead values indicate antistatic properties. It is suggested that a of only a single compound being present in any specific minimum of 10 megohms is required for antistatic polycomposition as is indicated by the respective formulae, vinyl chloride compositions (British Plastics, March each product consists of an equilibrium mixture of four 1956). isomers, with the structures of Formulae I and IV pre- (b) Thermal stability measurements.The compresseddominating. The various intramolecular rearrangements molded samples of the polymer containing the various occur along the following lines: anti-static agents were tested for thermal stability by ovenon /CHzCHOH-R" oc-R omorroHR" RCOCH2CH--CH2-N HOCHr-CH-CHr-N 0 CHgCHOH-R' CHZCHOHR o'cLa CHzCHOHR i OH CHzCHOHR RC-OCH2CH-CHz-N HOCHg-CH-CHg-N CHQCHOHR CHzCHOHR The present invention contemplates use of quaternary aging in a forced draft oven (Blue M Corporation) at salts of Formula I as well as the equilibrium mixtures 175 C. The samples were removed at five-minute interwhich result from the intramolecular shifting of the acyl vals and examined visually for discoloration.

groups. The results of the test are shown below in the table.

TABLE I.IN RIGID POLYVINYL CHLORIDE (1.5% CONC.)

H CHaCHzOH G9 R-C-O-CHz-CHOH-CHzN-CHzCHaOH Surface CH Resistivity Dlscoloratlon Oven-Aging at 175 0., Color (Minutes) CHSSOi R Acid Source Stearie 12 10 None (0)-... V. It. yel- Lt. yellow Yellow (15) Dk. yellow (9). (12). low (20);

Coconut .4 x10 "do ..do do ..do -...do

Synthetic Mixed Acid, C9-C1; X1 L- d0 o do 0 Rosin Acids (Hydrogenated) 45mm Ltyellow Lt. yellow- Yellow- Orange (20).

9 orgilge (()1r r i)nge Rosin 17x10 None (0).... Lt. yellow- (11) Yellow- (17) Dk. orange rggmge orange (25). N

None soxto -.do Trac e, yol- Lt. yellow The plastic materials for which the antistatic agents of i EXAMPLE 2 this invention are most valuable are those which by their nature are processed at high temperatures. Typical of Evaluation other polymers these are the polymers of monolefins of 2-4 carbons such The antistatic agents of this invention "were evaluated as ethylene and propylene, polyvinyl chloride, polystyrene as antistatic agents in polyethylene (both low andhigh and rubbery copolymers thereof, acrylics such as polydensity), polypropylene. and polymethyl methacrylate. methyl methacrylate, etc. The antistatic agents were incorporated into the polymers The present invention is illustrated by the following exby milling on a tWo-rolllaboratory mill at to 5 175 0., followed by compression-molding to give plaques of 2 x 2 /2 x 0.050 inches.

The antistatic properties 'of the prepared polymers were measured according to the procedure of Example 1 after conditioning for 24 hours at 50% relative humidity and 70 C.

This shows that the compound of the invention maintains its activity at low humidity, even at low concentrations. The commercial agent even at high concentrations is ineifective under low humidity conditions. At low concentrations and low humidity, the activity of the commercial agent is nil.

I H3 CH 0 H RCO-CH2CHOHGH7-NCH2CH2OH Substrate Cone. Surface Resistivity CH3 (Megohms) C H3504 Compound R Coconut Oil High Density Polyethylene. 0.5 25x10 Control Do... D0 D0 Do Do D EXAMPLE 3 TABLE III Surface Resistivity (megohrns) Percent Concentration This Invention Commercial 1. 45x10 15X10 1. 0 80X10 10 10 0. 5 20x10 10X10 0. 3 60x10 It can be noted that the agent of this invention maintains its activity at concentrations too low for the commercial agent to show activity.

EXAMPLE 4 In the table below is shown the etiect of low humidity on the retention of antistatic properties of an agent of this invention in rigid polyvinyl chloride. For comparison purposes results with a commercial quaternary ammonium agent are also shown. The agents are both the same as were used in Example 3.

TABLE IV Surface Resistivity (megohms) 50% Humidity 30% Humidity 1.5% This Invention 45x10 72x10 1.5 0 Cormnercial 10 30X10 0.5% This Invention. X10 13 1t 0.5% Commercial 10x10 Infinity We claim:

1. A polymeric composition having improved antistatic properties comprising (a) as the polymeric substrate a polyolefin, a vinyl chloride polymer, a styrene polymer or a polyacrylate, and (b) from 0.1 to 5% based on the weight of (a) of a quaternary compound of the formula:

wherein R is an aliphatic or a cycloaliphatic radical of eight to nineteen carbon atoms; R is a lower alkyl radical of 1-3 carbons and R" and R'" are individually either hydrogen or alkyl of 1-4 carbons; and X is an anion.

2. The composition of claim 1 wherein the polymer is polyvinylchloride.

3. The composition of claim 1 wherein the polymer is polyethylene.

4. The composition of claim 1 wherein the polymer is polypropylene.

5. The composition of claim 1 wherein the polymer is polymethyl methacrylate.

6. The composition of claim 1 wherein R is the acid radical of coconut acids, R is methyl, each of R and R" is hydrogen and X is methosulfate.

7. The composition of claim 1 wherein R is stearyl, R is methyl, each of R" and R' is hydrogen and X is methosulfate.

8. The composition of claim 1 wherein R is derived from C -C mixed neo-carboxylic acids, R is methyl, each of R" and R' is hydrogen and X is methosulfate.

No references cited.

JOSEPH L. SCHOFER, Primary Examiner.

HARRY WONG, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,399,178 August 27, 1968 Christos Savides et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below: 0 Column 1, line 51, after "compounding" insert a comma.

Column 2, lines 36 and 37, "the surface resistivity of the dried strip after it has been a solution of the compound in isopropanol and measuring" should read a solution of the compound in isopropanol and measuring the surface resistivity of the dried strip after it has been Columns 5 and 6, the table should be identified as TABLE II same table, first column, lines 3, 5 and 7 thereof, "Do", each occurrence, should read Coconut same table, same column, lines 4, 6 and 8 thereof, "Do", each occurrence, should read Control Signed and sealed this 27th day of January 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR. 

1. A POLYMERIC COMPOSITION HAVING IMPROVED ANTISTATIC PROPERTIES COMPRISING (A) AS THE POLYMERIC SUBSTRATE A POLYOLEFIN, A VINYL CHLORIDE POLYMER, A STYRENE POLYMER OR A POLYACRYLATE, AND (B) FROM 0.1 TO 5% BASED ON THE WEIGHT OF (A) OF A QUATERNARY COMPOUND OF THE FORMULA: 